AP Computer Science Principles covers how computing systems are designed, how data is represented and analyzed, how algorithms solve problems, and how the internet connects people and devices. Students need this cheat sheet to organize the major ideas, vocabulary, and exam language used across the course. It is useful for reviewing multiple-choice questions, the Create performance task, and common computing concepts that appear in real-world examples.
The core ideas include creative development, data, algorithms and programming, computer systems and networks, and the impact of computing. Important formulas and rules include bit count = number of binary digits, number of values with n bits = 2^n, and heuristic solutions trade guaranteed accuracy for speed or simplicity. Students should also know how abstraction, iteration, selection, lists, procedures, simulations, protocols, and cybersecurity practices connect across the course.
Key Facts
- The five AP CSP big ideas are Creative Development, Data, Algorithms and Programming, Computer Systems and Networks, and Impact of Computing.
- With n bits, a computer can represent 2^n different values.
- An algorithm is a finite set of step-by-step instructions that solves a problem or completes a task.
- Sequencing runs steps in order, selection uses a condition such as if or else, and iteration repeats steps using loops.
- A procedure with parameters supports abstraction because one named block of code can work with different input values.
- Lossless compression reduces file size while preserving all original data, while lossy compression removes some data permanently.
- The internet uses protocols, including TCP/IP and HTTP, so different devices and networks can exchange information reliably.
- Cybersecurity practices such as strong passwords, multifactor authentication, encryption, and software updates reduce risk but do not remove all risk.
Vocabulary
- Abstraction
- Abstraction is the process of hiding details to manage complexity, such as using a procedure name instead of rewriting all its steps.
- Algorithm
- An algorithm is a precise sequence of steps that can be followed to solve a problem or perform a computation.
- Binary
- Binary is a base-2 number system that uses only 0 and 1 to represent data in computers.
- Protocol
- A protocol is an agreed set of rules that devices use to communicate over a network.
- Simulation
- A simulation is a computational model used to imitate a real-world process or system.
- Heuristic
- A heuristic is a problem-solving approach that may find a good enough solution when an exact solution is too slow or difficult.
Common Mistakes to Avoid
- Confusing the internet with the World Wide Web, which is wrong because the internet is the network infrastructure while the web is one service that runs on it.
- Assuming more data always means better conclusions, which is wrong because biased, incomplete, or poorly collected data can still produce misleading results.
- Forgetting that lossy compression permanently removes data, which is wrong because a lossy file cannot always be restored to its exact original form.
- Writing an algorithm that works for only one example, which is wrong because an algorithm should correctly handle all valid inputs in the problem statement.
- Claiming encryption prevents all cyberattacks, which is wrong because encryption protects data confidentiality but does not stop phishing, weak passwords, or human error.
Practice Questions
- 1 How many different values can be represented using 8 bits?
- 2 A file is compressed from 50 MB to 20 MB. How many megabytes were saved, and what percent of the original file size was removed?
- 3 Given the values x = 7 and y = 3, what is printed by this algorithm: if x > y then print x - y else print y - x?
- 4 Explain why abstraction is important when writing programs with procedures, lists, or APIs.